1. Field of the Invention
The present invention relates to a communication system, and more particularly, to a WLL (Wireless Local Loop) system.
2. Background of the Related Art
In general, the WLL system has a wireless subscriber line between a subscriber and a base station, which can provide audio communication services, facsimile services, and data communication services. The WLL system is being developed in full scale as problems of frequency efficiency, radio channel quality, and build up cost per a subscriber are solved as the technologies developed in 1980s for semiconductor and radio communication are combined with the radio frequency technology developed in 1970s.
In comparison to a conventional wire network, the WLL system has advantages including low start up cost and time, and maintenance cost, and the WLL system can provide a variety of services, such as high communication quality, data, and an ISDN (Integrated Service Digital Network) and the like. The WLL system can be applicable when a new communication service provider intends to secure a subscriber network quickly, or the WLL system can be used as a communication infrastructure of a developing country, which has a poor wire communication network.
A basic WLL system is provided with telephone sets and an NIU (Network Interface Unit) which allows a radio communication between the telephone sets and a switchboard. A separate type WLL system and a integrate type WLL system are available in the WLL system. The separate WLL system is provided with an NIU for wire connection to a stationary telephone so that the subscriber who has the stationary telephone set connected to an existing wire network can buy, not a telephone set, but the NIU only when the subscriber subscribes to the WLL system. The integrated WLL system is provided with the telephone set and the NIU integrated in hardware basis for the convenience of the subscriber who has no stationary telephone set in subscription to the WLL system.
FIG. 1 illustrates related art separate type and integrate type WLL systems. The related art separate type and integrate type WLL systems are provided with a stationary telephone set 10 installed in a house or office, and an NIU 20 connected to the stationary telephone 10 for transmission/reception of information over a radio interface, an integrated type telephone set 30 having the NIU 20 built-in, respectively. A base station 40 connects to the NIU 20 or to the integrated type telephone set 30, and a base station controller 50 is wire connected to the base station 40 for processing a call and transmitting a message. An operating apparatus 60 operates and maintains the WLL system. The base station controller 50 is connected to a switching center 70.
The operation of respective units of the aforementioned WLL system will be explained. The NIU 20, connected to a last stage of the WLL system, conducts radio frequency transmission/reception functions for transmission/reception of information over a radio interface, a base band signal processing function for conducting a function for transmitting a signal converted from radio frequency into a base band to the subscriber and a function reverse of the foregoing function, a function for processing a signal protocol with a communication network, and a function for processing an audio signal. The base station 40 makes a radio connection to the NIU 20 or the integrated type telephone set 30, to processes a radio frequency signal to conduct functions of radio signal modulation/demodulation, and channel coding/decoding, and is wire connected to the base station controller 50 through a particular trunk (EI/HDSL).
The base station controller 50 is positioned between the base station 40 and the switching center 70 for controlling various base stations, and conducts a signal message transmission function, a call processing function, a code converting function, and an interfacing function between the base station and the switching center 70. The operating apparatus 60 is in charge of operation and maintenance of the NIU 20, the base station 40, and the base station controller 50, and conducts a network system managing function, network element managing function, a performance managing function, a data processing function, a software managing function, and a security managing function.
The transmission operation of the aforementioned WLL system will be explained. First, an originating side subscriber inputs a destination telephone number to the stationary telephone 10. The NIU 20 connected to the stationary telephone 10 receives the destination number, modulates it into a radio frequency, and transmits it to the base station 40. In this instance, under the present radio environment, the NIU 20 transmits the destination telephone number to the base station 40 en-bloc, or functional address signalling, wherein incoming destination telephone number is stored in a memory in succession, and the stored destination telephone number is transmitted to the base station at one time by means of an originating operation, such as pressing a xe2x80x9cSENDxe2x80x9d key or transmitting after a preset time is lapsed, or the like. The integrated type telephone station 30 also transmits the destination telephone number to the base station en-bloc once the destination telephone number is provided thereto.
The base station 40 transmits the destination telephone number to the switching center 70, and the switching center 70 determines the destination subscriber of being within its own area or an area of other switching center, to determine a communication path, and transmits a signal for setting up the communication path and the data to the destination subscriber, to set up a call between the origination subscriber and the destination subscriber.
The aforementioned WLL system has various problems. For example, there has been inconvenience of the additional pressing of xe2x80x98SENDxe2x80x99 button, or other originating operation required for the en-bloc transmission in the call set up after the originating subscriber presses all the destination telephone numerals. Further, the delay before completion of call set up, starting from assignment of communication channel to connection of a communication path between subscribers, coming from such a pressing of xe2x80x98SENDxe2x80x99 button or other originating operation causes a delay in a communication service.
An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
An object of the present invention is to set up a call in a WLL system by using an overlap dialing during off hook of a station.
One object of the present invention is to provide a method for setting up a call in a WLL system, which can reduce a call setting up time period and solve the inconvenience of pressing xe2x80x9cSENDxe2x80x9d button.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the method for setting up a call in a WLL system having mobile stations, a base station and a switching center, including the steps of (1) if the mobile station is in an off hook state, the mobile station transmitting an origination message to the base station and assigning a traffic channel between the mobile station and the base station, (2) the mobile station transmitting a destination telephone number to the base station, and (3) the switching center connected to the base station connecting a call to a destination mobile station according to the destination telephone number.
In other aspect of the present invention, there is provided a method for setting up a call in a WLL system having mobile stations, a base station and a switching center, including the steps of (1) if the mobile station is in an off hook state, the mobile station detecting reception of a first digit of a destination telephone number, (2) upon detecting reception of the first digit, the mobile station transmitting an origination message to the base station and assigning a traffic channel between the mobile station and the base station, (3) the mobile station transmitting a destination telephone number to the base station, and (4) the switching center connected to the base station connecting a call to a destination mobile station according to the destination telephone number.
The step (3) includes the steps of the mobile station storing the destination telephone number received before the step (2) therein, and, upon assignment of the traffic channel, the mobile station transmitting the destination telephone number at first, and transmitting the destination telephone number received after the assignment of the traffic channel to the base station.
The destination telephone number received after the assignment of the traffic channel is transmitted one by one in real time, and the destination telephone number is transmitted from the mobile station to the base station in a burst DTMF message.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.